Cheescutters, Eggslicers and Motorcyclists Wire Rope Safety Barriers and the risks posed to Motorcyclists. Nicholas Rodger Dip.Eng (Civil), GIPENZ

Transcription

1 Cheescutters, Eggslicers and Motorcyclists Wire Rope Safety Barriers and the risks posed to Motorcyclists Nicholas Rodger Dip.Eng (Civil), GIPENZ

2 Background Recent years have seen growing concern amongst motorcyclists about the safety of Wire Rope Safety Barriers (WRSB) in crashes involving motorcyclists. A recent high profile crash fuelled these concerns. It will be demonstrated that the actual risk from WRSB is appropriate, given the no barrier alternative, and that the barriers are a safe, appropriate treatment, notwithstanding emotive appeals.

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4 This is not just a NZ issue. Motorcyclists will continue to be killed by wire median strips if road authorities fail to review their "prehistoric" designs with a reputation for leaving riders with severed limbs - Head of the NSW Motorcycle Council, Guy Stanford, Motorcyclists Advocacy Groups around the world are vocal in their opposition to WRSB. INSERT IMAGE HERE It seems perverse that a safety system has been designed which actually increases the likelihood of a fatality. Not only is the wire rope itself dangerous to motorcyclists, but its numerous upright support posts can also be lethal to riders. - British Motorcyclists Federation

5 They (The Motorcycling Community) say With reference to wire-rope barriers, they are fatal for motorcyclists. A recent study in Scotland showed that out of 7 impacts last year there were 7 motorcyclist fatalities. That s 100%. British Motorcycle Federation all motorcyclists' organisations in Europe are strongly opposed to the use of cable barriers - Federation of European Motorcyclists (FEMA) They're deadly for motorcyclists, we've seen eight killed that we know of on wire rope barrier sites," - Motorcycle Riders Association (Australia)

6 They (The Motorcycling Community) say

7 We (the Engineering Community) Say There is no conclusive evidence to suggest that wire rope median barriers will make roads more unsafe for motorcyclists. Transit NZ Sweden, with over 600 km of flexible barriers on its roads does not have any records of motorcycles being sliced by the barriers. Monash University Accident Research Centre We have not seen any proof that wire-rope barriers are more dangerous than other types of barriers with posts. the barriers are installed in order to protect something that is worse to hit than the barrier - Swedish National Road and Transport Institute.

8 Q: How big a problem are we looking at here? A: Lets put things in perspective o 174 Motorcyclist fatals inclusive (previous 5 years) o 34 were coded struck objects o 3 of these were coded Guard Rail (1 WRSB, 1 W- Section, 1 Bridge Rail) During the study period ( inclusive), there were a total of 77 reported injury / fatal crashes between motorcycles and guard rails, with: o 3 Fatal, o 28 Serious, o 46 Minor crashes.

9 Q: Are WRSB as lethal as opponents claim? A1: The short answer is No. A2: The slightly longer answer is we can't accurately tell one way or the other. In the preceding 5 years, two serious and one fatal crashes have involved WRSB. Rather than decapitation and lethal injuries, the two (coded as Serious) crashes resulted in a fractured ankle in one case, and grazes and the loss of the tip of the large toe in the other. Although it is difficult to derive accurate conclusions from the small number of NZ crashes, research has been conducted overseas.

10 Are WRSB as lethal as opponents claim? (continued) INSERT IMAGE HERE

11 Studies on Motorcycle Collisions with Barriers have been conducted Barrier Type (impact angle) Dominant Injury Mechanism's Observed Outcome Primary Injury Risk Secondary Injury Risk W-Section (horiz.) Impact with posts High impact to head, chest and shoulder High Moderate W-Section (upright) Impact with posts, impact onto road High impact to head Minor Moderate Concrete (horiz.) Collision with barrier High impact to head High Minor Concrete (upright) Secondary collision with road / oncoming vehicle Little deceleration, overtopped barrier Minor Moderate WRSB 12 ) Impact with posts, impact with road High impact to chest, extremities. Moderate impact to head High Moderate WRSB 25 ) Impact with posts, impact with road High impact to head, chest and extremities High High (High is defined as exceeding biomechanical limits; moderate as high values but under limits, with minor being low values) (Primary Injury = injuries sustained upon impact with barrier< Secondary injury = all injuries after primary) Table 1. Crash test summary (all crashes at ~60km/hr) (Rodger, 2008, Berg et al, 2005)

12 Studies on Motorcycle Collisions with Barriers have been conducted (continued) all sliding collisions with barriers occurring at open road speeds are likely to result in severe to fatal injuries to riders Upright collisions with barriers are likely to result in minor to fatal injuries W-Section and Concrete can be considered to have broadly similar motorcycle compatibility, with WRSB being less compatible Unlike W-Section, all collisions with WRSB result in posts being struck, increasing the injury risk (Rodger, 2008)

13 Q: So why do we install WRSB, if Concrete Barriers are more forgiving to motorcyclists? A: Because they are typically safer for vehicle occupants than other barrier systems. Concrete barriers, while very effective in preventing cross-over crashes, impart high deaccelerative forces on vehicle occupants, and inflict sever damage on vehicles in collisions. Studies have shown that concrete barriers are out-performed by WRSB in areas such as energy dissipation, deflection levels and forces experienced by vehicle occupants. (Monash University Accident Research Centre MUARC) Steel W-section guard rails, although more forgiving to vehicle occupants still impart high deaccelerative forces, and have potential to cause serious injury through inappropriate end terminals.

14 Q: They're not Cheesecutters then? A: No unless you collide with one at 150 km/hr Rather than being sliced by the cables, motorcyclists are injured in collisions with posts, and when they and their motorcycle become tangled in the cables. INSERT IMAGE HERE Due to this post profiles have been modified from the original H posts to the current S posts, which present a blunter, curved face to riders.

15 Q: So why have barriers at all? They kill people.. A road safety barrier is considered to be a hazard, and should only be used when the consequences of hitting it are less than the hazard/object it is shielding. The use of a road safety barrier should only be considered as a last resort following an assessment of whether or not the mitigation of the hazard or object can be achieved through the application of the principles of clear zoning - TNZ M/23 Notes on the specification for road safety barrier systems

16 Q: So why have barriers at all? They kill people (continued) A: Because overall they are safer to hit, than the objects they are shielding. Crash barriers, whilst affecting the outcome of a crash will not increase the risk that a motorcyclist will crash. Overall the risk of a motorcyclist is considered greater without a crash barrier than it is with it.

17 So crash barriers are a necessary evil. What can we do to increase their compatibility with motorcyclists? INSERT IMAGE HERE Proprietary retrofittable products have been developed by European manufacturers. These devices attach to the posts of WRSB (and W-Section) and prevent impact with the supporting posts. Covers for the cables, have been proposed, but these ignore the posts, and therefore cannot be recommended.

18 Q: So where do we start? A: We don t need to retrofit the entire barrier asset (and certainly can't afford to) The Crash Analysis System (CAS) was interrogated for on all serious and fatal injury crashes involving motorcycles and guardrails over the past 5 years ( inclusive). Detailed crash by crash analysis was performed on the 31 individual (serious and fatal) Traffic Crash Reports (TCR's) to establish trends for parametric analysis and comparison.

19 Q: Where / how are the crashes happening? A: The accompanying tables summarise the findings. Trends identified: o Rural environment o 100 km/hr speed limit o Right hand turn o Single vehicle o Weekend (58%) o Dry Road (94%) o W-Section struck Crash Location Percentage Composition Right-hand corners 64% Left-hand corners 18% Straight sections 18% Table 2. Road Geometry at Crash sites. (Rodger, 2008) Percentage Composition Motorcycle upright upon impact 46% Motorcycle horizontal upon impact 54% Table 3. Motorcycle attitude upon impact. (Rodger, 2008) Barrier Type Serious Crashes Fatal Crashes Concrete 0 0 Steel W Section 27 2 WRSB 2 1 Other (sight rail etc) 2 0 Table 4. Frequency of serious / fatal crashes. (Rodger, 2008)

20 Q: Where / how are the crashes happening? Analysis of crash data suggests that median barrier crashes are uncommon, and generally have better outcomes than entering the opposing traffic lane. INSERT IMAGE HERE The dominant crash type, is single vehicle loss of control on right hand bend, colliding with W-Section steel guardrail.

21 Q: So WRSB isn't the problem? A: In statistical terms, no. The 3 crashes into WRSB were all median treatments, with the two serious crashes likely to have had the same outcome regardless of the barrier type. As previously mentioned, the fatal involving WRSB, would have been fatal no matter what barrier type was involved, due to the speeds involved. Had no barrier been installed, encroachment into oncoming traffic would almost certainly have occurred.

22 So where to from here? In situations where WRSB is installed as a side of road treatment, simple guidelines could reduce the risk to motorcyclists, without detracting from its performance with larger vehicles. Assuming clear-zoning is not possible: No installs of unmodified WRSB on broken-back or low radii corners (<250m), as analysis shows these are most frequently struck by motorcyclists. On intermediate radii corners ( m) on known motorcycle routes, installation of barriers with additional lower rail to prevent post impact. (It may be worth considering W-Section with lower rail treatment in these areas)

23 Conclusion WRSB is a proven barrier treatment, which safely arrests vehicles with low deaccelerative forces, is easily repaired, and highly cost efficient. In un-modified form it has the potential to inflict serious injuries on motorcyclists, but these need to be balanced against the likely injuries had the barrier not been there, and the benefits to the general motoring public. Further research is needed to establish the true risks of WRSB as installed in the NZ environment, so that definitive conclusions as in-service performance can be made.